It is known in the art of electroplating to use frames on which are removably anchored plates or the like articles to be plated, for holding them while they are being submerged in large acid tanks or baths, e.g. for creating circuit boards. The acid bath is one of several steps involved in the manufacture of a printed circuit board. The acid solution is usually either chloridric acid or sulfuric acid. The overhanging frames are made of an electrically conducting material sealed in a fluid-tight and electrically insulating material to substantially slow down the corrosive effects of the acidous vapors from the bath of acid, and are sealingly electrically connected to the articles to be plated. The frames are connected to a cathode element, or flight bar, and are subjected to an electrical current which is transmitted through the frame structure, the article and the liquid acid. An anode element is also submerged in the acid bath, spaced 6 to 10 inches from the circuit board. The potential difference between the article and the reducing agent anode element allows the metal composing the latter to migrate and attach itself onto the article. The metal composing the anode element can be for example copper, or any other suitable material combining a proper oxydo-reduction potential and suitable conductive characteristics.
A device as generally described above is disclosed in Canadian patent No. 1,215,939 issued Dec. 30, 1986, with two of the three joint inventors therein being the two joint inventors of the present patent application. The device of the '939 patent indeed comprises a large frame on which can be sealingly bolted a number of articles to be plated, as shown in FIG. 3 of this patent. The electrical current is transmitted through the threaded shaft in FIG. 3, the shaft engaging a bore in the article to be plated and thus conducting the electrical current through this engagement. An electrical insulator covers the plate holding member and the article is thus sealingly engaged on both sides around the electrically conductive threaded shaft.
The device according to the '939 patent comprises three main disadvantages. Firstly, the article to be plated has to be bored therethrough to accommodate the threaded shaft therein. Without this through bore, the article cannot be held by the rack in the acid bath. Secondly, the nut head portion 50 of the holding bolt has to be manually screwed into place and manually removed to install/retrieve the article. This can be a very time-consuming operation, since there can be many such bolts on a single rack as shown in FIG. 1, and moreover there can be many such racks being submerged into the acid baths. Also, screwing/removing an important number of nut heads often results in wrist pain for the worker and can and do lead to claims for insurance disability coverage. Thirdly, the nut head portion of the holding bolt is submerged in the acid bath and then has to be directly manipulated to remove the plated article therefrom. Since the acid bath comprises a poisonous and dangerous liquid, it is clearly not desirable to manipulate directly these nut heads; protective gloves or the like have to be used, and these gloves can become cumbersome and backward in removing the small nut head.
Another invention is shown in U.S. Pat. No. 2,190,440 issued in 1940 to W. Beebe, wherein a rectangular frame holds a number of inwardly oriented clamp members illustrated in FIG. 3. The clamp members have an electrically conductive fixed jaw and an insulative jaw that are biased into a closed position, over the article to be plated, thus holding the latter at the center of the frame. The electrically conductive jaw is sealingly and conductingly connected to the article, but is otherwise covered by an insulative layer. The two jaws are biased into a closed position by means of elastic rubber bands linking them.
The device disclosed in the Beebe patent comprises three important disadvantages. Firstly, the dimension of the whole frame has to be modified to accommodate articles (plates, in this case) of different sizes. This can be highly time-consuming, and is of course not desirable. Secondly, the small clamp members are submerged in the dangerous liquid acid bath, and then have to be manipulated directly to allow the plate to be retrieved. Thus, gloves or other protective gear have to be worn, effectively reducing the preciseness of the manipulation and being cumbersome in operating the small clamp members. Thirdly, four clamps have to be operated to install/remove a single plate from the frame, significantly increasing the time to accomplish these operations.